Fourier transform near-infrared (FT-NIR)
spectroscopy combined
with a partial least-squares (PLS) model was successfully employed
to study the hydrolysis kinetics of dimethyldiethoxysilane, methyltriethoxysilane,
and tetraethoxysilane in an acid-catalyzed EtOH system. The high scanning
speed and high sensitivity of FT-NIR spectroscopy enabled the new
method to catch the rapid changes of the H<sub>2</sub>O and EtOH concentrations
without delay, allowing the kinetic behaviors of the hydrolysis reactions
of the specified alkoxysilanes to be investigated. The hydrolysis
processes were found to follow second-order reactions. The hydrolysis
rate constants, activation energies, and Arrhenius frequency factors
were obtained. The FT-NIR PLS results were in good agreement with
those determined by Fourier transform midinfrared spectroscopy. However,
the FT-NIR PLS method was found to be more accurate, because of the
powerful data processing ability of PLS. All of the results suggest
that the FT-NIR PLS model is a valuable tool for performing kinetic
research.